1. Field of the Invention
This invention relates to a numerical control system and, more particularly, to a numerical control system equipped with a computerized man-machine interface controller (MMC unit) having at least a CRT and a keyboard.
2. Description of the Related Art
In a numerical control system, a programmable machine controller (referred to as a "PMC unit") executes predetermined sequence control on the basis of a command from a numerical control unit (NC unit), whereby the various elements of a machine tool operate based on the results of sequence processing. The NC unit waits for the completion of machine element operation before executing the next numerical control operation. NC program data is obtained from an NC tape or memory or is inputted from a manual data input unit equipped with a CRT (which unit is referred to as a CRT/MDI unit).
In addition to having a function which allows NC data to be inputted manually, the CRT/MDI unit is adapted to display various pictures on the CRT screen, these including e.g. machine present position, program contents, offset quantities, parameters, the contents of alarms, setting data and the like, and to set, modify or reset various data by prescribed manipulation of keys on the keyboard.
FIG. 4 is a block diagram of a conventional numerical control system. Numeral 101 denotes an NC tape (or other medium) in which NC data are punched, 102 a tape reader, 103 a RAM for storing NC data and the results of processing, 104 a ROM storing a control program, 105 a processor, 106 an axis controller for executing pulse distribution calculations and the like upon receiving inputs of traveling distances along respective axes per predetermined periods of time, 107 a CRT/MDI, 108 an interface circuit, 109 a parameter memory, and 110 an EROM (erasable ROM) storing a sequence program. The single processor 105 of this numerical control system executes all of the following processing:
(1) numerical control processing based on NC program data;
(2) sequence control processing based on the sequence program; and
(3) data input/output processing using the CRT/MDI unit 107.
For this reason, the processor is under a heavy load and is incapable of fine processing, processing with a quick response, and processing which is complicated.
Accordingly, as shown in FIG. 5, a numerical control system has been proposed in which the NC unit, PMC unit and CRT/MDI unit are separated from one another, a common memory is provided and various control operations are performed by an exchange of data among these units via the common memory.
In FIG. 5, numeral 1 denotes the NC unit, 2 the machine tool, 3 a PMC unit, 4 a CRT/MDI unit, 5 a servo unit, and 6 a data exchange controller having a common memory (RAM) 6a, bus controller 6b and serial transfer controller 6c.
The NC unit 1 has a processor 1a, ROM 1b, RAM 1c, NC data input/output unit 1d and axis controller le. The PMC unit 3 has a processor 3a, a ROM sequence program and software created by the user, a RAM 3c for storing the results of sequence processing in addition to parameters and various tables, a digital signal input unit 3d, a digital signal output unit 3e, and a serial transfer controller 3f.
The CRT/MDI unit 4 has a keyboard 4a, a CRT 4b, a keyboard controller 4c, a CRT controller 4d, and a serial transfer controller 4e.
FIG. 6 is a view showing the concept of the numerical control system illustrated in FIG. 5, in which portions similar to those of FIG. 5 are designated by like reference characters.
In accordance with this numerical control system, the NC unit 1 and PMC unit 3 are each provided with their own processors, so that the processor 1a need not execute sequence control. The makes it possible to reduce the burden on the processor.
Further, the side that transmits data writes the data and commands that are to be transmitted into the common memory 6a via the bus controller 6b. The side that receives the data reads the data addressed to it out of the common memory 6a, in which these data have been written. If processing is executed in this manner, the exchange of data can be controlled at high speed.
In addition, since the PMC unit 3 is provided with the processor 3a and is capable of exchanging data with the NC unit 1, control special to the maker can be performed, in addition to the conventional PMC function, by preparing the prescribed software and storing it in the ROM 3b. For example, predetermined control can be carried out upon receiving various data necessary for NC control, such as present positions along the respective axes or modal data, from the NC unit 1, or a non-volatile memory (not shown) such as a bubble memory connected to the NC unit can be utilized.
The PMC unit 3 is also capable of exchanging data with the CRT/MDI unit 4 via the data exchange controller 6. The PMC unit 3 therefore can
(1) read data set by the keyboard 4a, and
(2) display ladder diagram and the like on the CRT 4b.
FIG. 6 illustrates, in conceptual form, the previously proposed numerical control system depicted in FIG. 5 and shows that there is a strong relationship between the CRT/MDI unit 4 and the NC unit 1 or PMC unit 3. Consequently, it is necessary to design the NC unit and PMC unit upon taking the functions of the CRT/MDI unit into consideration. Hence, when a display function or control function peculiar to the CRT/MDI unit is required, a new NC unit or PMC unit must be designed each time. This is undesirable.
Furthermore, since the CRT/MDI unit does not possess an intelligent function, data must be processed on the side of the NC unit 1 or PMC unit 3, thereby increasing the burden on these sides. In the end, a CRT/MDI unit exhibiting fine control cannot be provided.
In addition, with the numerical control system of FIG. 5, there is a limitation on complicated processing, though the processing that can be executed is more complicated than with the system of FIG. 4. Specifically, automatic programming processing, full self-diagnostic processing, CRT instruction manual-type display processing and other forms of complicated processing cannot be executed.